Abstract
Goal. Attention can be oriented externally to environmental stimuli or internally to memory representations. Both types of attention can modulate visuospatial working memory performance and engage overlapping cortical areas. While the spatial profile of external attention has been characterized, the profile of internal attention remains unclear. Using a pre-cue and retro-cue paradigm, we investigated the spatial profile of both external and internal attention. Methods. We presented memory arrays consisting of six disks with random colors, evenly distributed on an imaginary circle. After the array, a probe disk appeared at the same location of one of disks in the array. Participants adjusted the probe's color until it matched the color of the memorized disk in that location. External and internal attention was manipulated using a predictive pre-cue or retro-cue, respectively. The cue correctly indicated the probe location in half of the trials; for the remaining trials, the cue could indicate an item at a location that was either 1, 2, or 3 items away from the probe. Memory performance was measured as the absolute angular difference on a color wheel between the recalled and presented color. The baseline (no-cue) condition was included to assess attentional modulation. Results. External attention reduced memory error on valid trials, but in a non-monotonic pattern as a function of cue-target distance; that is, the largest error was observed at the intermediate distance, but a smaller error was observed at the farthest cue-target distance. This implies a surround suppression mechanism of external attention. Importantly, we found a similar non-monotonic pattern for internal attention, in which performance was the worst at the 2-item distance but rebounded for the farthest distance. Conclusion. Our results demonstrate surround suppression for both internal and external attention. Attention may select internal representations in a similar way as selecting stimuli in the environment.
Meeting abstract presented at VSS 2018